Edge-lighted signs are well known to those skilled in the art. Thus, U.S. Pat. No. 3,349,511 discloses an illuminated sign comprised of a sheet of glass or plastic in which a light source is positioned at the edge of the sheet in order to direct light longitudinally throughout the sheet. The patentee teaches that "in the prior art, longitudinally lighted devices use the effect and construction known as edge lighting. In this construction, a transparent sheet of rigid material such as glass or plastic is illuminated by means of lamps or the like at points around the periphery of the transparent sheet. The light from the light source is transmitted longitudinally, i.e., planar to the major surfaces of the sheet. The lighted displays in the prior art are not efficient in utilizing the light longitudinally transmitted through the sheet and such inefficiency results in a display of non-uniform reflection, low contrast, and derivatively poor visibility."
Many of the prior art illuminated signs utilize a substantial amount of electricity during operation and, thus, must incorporate expensive circuitry to shut them off in the daytime. Thus, for example, U.S. Pat. No. 3,406,475 discloses a rectangular, illuminated sign comprised of a lamp which is connected in an electric circuit connected by a light-sensitive cell for breaking the circuit during the daytime. Thus, for example, U.S. Pat. No. 4,386,476 discloses an edge-lighted display sign which comprises a variable duty cycle oscillator to control the lamp in the sign.
U.S. Pat. No. 3,179,902 discloses an edge-lighted sign which can be allowed to remain continuously on and is powered from an a.c. source. However, the apparatus of this patent must comprise a transformer located within the apparatus to step down the voltage to the incandescent lamps used in the sign.
It is an object of this invention to provide an edge-lighted sign with excellent visibility during both the daytime and nightime.
It is another object of this invention to provide an edge-lighted sign which can be allowed to stay on all the time but which consumes only a minimal amount of electrical power.
It is yet another object of this invention to provide an edge-lighted sign which has a simple, inexpensive design and need not comprise a transformer, a light-operated on-off switch, or other complex components.